I found an interesting bug when trying to query for a Campaign based on the NumberSent field. When executing the following query I'm receiving 'Illegal Integer' error:
system.debug([select id from Campaign where NumberSent = 5544022491]);
However, when I change the number e.g. to 1544022491, the query works. It seems like a Salesforce issue. What are your thoughts? Worth to mention is that I'm facing the same issue no matter what field of type Number I use in the SOQL for the filter.